On 02/09/2022 16:14, Abel Vesa wrote:
Currently, there is a race window between the point when the mutex is
unlocked in fastrpc_map_lookup and the reference count increasing
(fastrpc_map_get) in fastrpc_map_find, which can also lead to
use-after-free.
So lets merge fastrpc_map_find into fastrpc_map_lookup which allows us
to both protect the maps list by also taking the &fl->lock spinlock and
the reference count, since the spinlock will be released only after.
Add take_ref argument to make this suitable for all callers.
Fixes: 8f6c1d8c4f0c ("misc: fastrpc: Add fdlist implementation")
Co-developed-by: Ola Jeppsson <ola@xxxxxxxx>
Signed-off-by: Ola Jeppsson <ola@xxxxxxxx>
Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
---
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
drivers/misc/fastrpc.c | 41 +++++++++++++++++++++--------------------
1 file changed, 21 insertions(+), 20 deletions(-)
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 93ebd174d848..0c816a11eeec 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -333,30 +333,31 @@ static void fastrpc_map_get(struct fastrpc_map *map)
static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,
- struct fastrpc_map **ppmap)
+ struct fastrpc_map **ppmap, bool take_ref)
{
+ struct fastrpc_session_ctx *sess = fl->sctx;
struct fastrpc_map *map = NULL;
+ int ret = -ENOENT;
- mutex_lock(&fl->mutex);
+ spin_lock(&fl->lock);
list_for_each_entry(map, &fl->maps, node) {
- if (map->fd == fd) {
- *ppmap = map;
- mutex_unlock(&fl->mutex);
- return 0;
- }
- }
- mutex_unlock(&fl->mutex);
-
- return -ENOENT;
-}
+ if (map->fd != fd)
+ continue;
-static int fastrpc_map_find(struct fastrpc_user *fl, int fd,
- struct fastrpc_map **ppmap)
-{
- int ret = fastrpc_map_lookup(fl, fd, ppmap);
+ if (take_ref) {
+ ret = fastrpc_map_get(map);
+ if (ret) {
+ dev_dbg(sess->dev, "%s: Failed to get map fd=%d ret=%d\n",
+ __func__, fd, ret);
+ break;
+ }
+ }
- if (!ret)
- fastrpc_map_get(*ppmap);
+ *ppmap = map;
+ ret = 0;
+ break;
+ }
+ spin_unlock(&fl->lock);
return ret;
}
@@ -703,7 +704,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
struct fastrpc_map *map = NULL;
int err = 0;
- if (!fastrpc_map_find(fl, fd, ppmap))
+ if (!fastrpc_map_lookup(fl, fd, ppmap, true))
return 0;
map = kzalloc(sizeof(*map), GFP_KERNEL);
@@ -1026,7 +1027,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
for (i = 0; i < FASTRPC_MAX_FDLIST; i++) {
if (!fdlist[i])
break;
- if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap))
+ if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap, false))
fastrpc_map_put(mmap);
}
